title: Refinement of triclinic lysozyme: II. The method of stereochemically restrained least squares.
abstract: Refinement of triclinic lysozyme by restrained least squares against the 2 A resolution X-ray data is described, beginning with the model from cycle 17 of the preceding paper [Hodsdon, Brown, Sieker & Jensen (1990). Acta Cryst. B46, 54-62]. After 20 refinement cycles, R stood at 0.172. Nevertheless, serious errors involving both main-chain and side-chain atoms still remained, requiring numerous model rebuilding sessions interleaved with refinement cycles. After 63 cycles R = 0.124 for the model which includes all protein atoms, 249 water oxygen sites and five nitrate ions. Although the overall B is relatively low, 10.5 A2, B's for atoms in the region of residues 101-103, toward the termini of some of the longer side chains, and in the region of the C terminus of the main chain exceed 20 A2, indicating relatively high atomic mobilities, disorder, or remaining errors in the model.
authors.affiliation: Neutron Physics Division, Bhabha Atomic Research Centre, Trombay, Bombay, India.
authors.forename: M
authors.initials: M
authors.lastname: Ramanadham
authors.forename: L C
authors.initials: LC
authors.lastname: Sieker
authors.forename: L H
authors.initials: LH
authors.lastname: Jensen
mesh_terms: D003198:Computer Simulation; D016018:Least-Squares Analysis; D008956:Models, Chemical; D009113:Muramidase; D011487:Protein Conformation; D014961:X-Ray Diffraction
chemical_list: D009113:Muramidase